On the role of shear in cosmological averaging

Using the spherically symmetric inhomogeneous Lemaitre-Tolman-Bondi dust solution, we study how the shear and the backreaction depend on the sharpness of the spatial transition between voids and walls and on the size of the voids. The voids considered here are regions with matter density Omega ~ 0 and expansion rate Ht ~ 1, while the walls are regions with matter density Omega ~ 1 and expansion rate Ht ~ 2/3. The results indicate that both the volume-average shear and the variance of the expansion rate grow proportional to the sharpness of the transition and diverge in the limit of a step function, but, for realistic-sized voids, are virtually independent of the size of the void. However, the backreaction, given by the difference of the variance and the shear, has a finite value in the step-function limit. By comparing the exact result for the backreaction to the case where the shear is neglected by treating the voids and walls as separate Friedmann-Robertson-Walker models, we find that the shear suppresses the backreaction by a factor of (r_0/t_0)^2, the squared ratio of the void size to the horizon size. This exemplifies the importance of using the exact solution for the interface between the regions of different expansion rates and densities. The suppression is justified to hold also for a network of compensated voids, but may not hold if the universe is dominated by uncompensated voids.Comment: 17 pages, 3 figure

The induced Chern-Simons term at finite temperature

It is argued that the derivative expansion is a suitable method to deal with finite temperature field theory, if it is restricted to spatial derivatives only. Using this method, a simple and direct calculation is presented for the radiatively induced Chern-Simons--like piece of the effective action of (2+1)-dimensional fermions at finite temperature coupled to external gauge fields. The gauge fields are not assumed to be subjected to special constraints, and in particular, they are not required to be stationary nor Abelian.Comment: 5 pages, REVTEX, no figure

Non-Alcoholic Fatty Liver Disease as Risk of Cardiovascular Disease: Myth or Reality?

Nonalcoholic fatty liver disease (NAFLD) includes a wide spectrum of liver conditions ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) and advanced hepatic fibrosis. Taking into account that NAFLD shares many common risk factors with cardiovascular diseases, it is evident that NAFLD may promote to increased cardiovascular morbidity and mortality.Cumulative evidence suggests that NAFLD is linked to atherosclerosis, coronary artery disease, obesity, type 2 diabetes, and also predicts the clustering of risk factors for cardiovascular diseases.To our opinion, the role of NAFLD in the prediction of cardiovascular risks should be investigated for coronary artery disease (CAD) prognosis assessmentThis review focuses on the pathophysiologic relationships between NAFLD and cardiovascular diseases, subclinical and clinical cardiovascular manifestations in NAFLD

Cardiopulmonary Microcirculation and Gas Exchange in Acute Adrenaline-Induced Injury

Microcirculatory alterations lead to cell and organ dysfunction. High levels of catecholamines induce tachycardia, coronary vasospasm, microcirculatory disruption, hypoxia, ventricular fibrillation. Hypercatecholaminemia increases pulmonary capillary resistance and permeability as well.Aim of this research is to study adrenaline-induced alterations in myocardial and lung microcirculation, and gas exchange parameters in rats.Experiments were performed in male Wistar rats divided into 2 groups: control (n=11), and animals (n=12) treated with histotoxic-dose adrenaline. Anesthetized animals were exposed to mechanical lung ventilation at a frequency of 40 breaths/min and were sacrified 20 min after adrenaline injection. Paraffin-embedded myocardial and lung tissues were stained by hematoxylin and eosin. Myocardial and pulmonary microcirculation was studied by Sisakyan and Chilingaryan methods for revealing intraorganic MCB based on detection of phosphatase enzymes’ activities (acid phosphatase and Ca2+-ATP-ase, respectively) in the vessel walls. Mean capillary diameter (MCD) was calculated using ocular-micrometer. Partial pressures of arterial blood O2, CO2 and pH were measured.Histological studies showed that adrenaline induced contraction band lesions of cardiomyocytes, diffuse pulmonary infiltrations, hemorrhages. Myocardial and lung microcirculation studies revealed inhomogeneous and less intensive staining, tortuous course of capillary walls and their destructive changes. Blood gas analysis data indicated hypoxemia and hypercapnia developing along with acidosis following adrenaline injection.In conclusion, high-dose adrenaline induces acute myocardial and lung injuries, manifested in inflammatory and microcirculatory alterations, disorders of pulmonary gas exchange that may aggravate further development of cardiopulmonary pathology. The data achieved in present study may allow further adjustment of treatment strategies for stress-induced myocardial injury considering the role of lung microcirculation and gas exchange disorders in the given pathology

Two-loop HTL Thermodynamics with Quarks

We calculate the quark contribution to the free energy of a hot quark-gluon plasma to two-loop order using hard-thermal-loop (HTL) perturbation theory. All ultraviolet divergences can be absorbed into renormalizations of the vacuum energy and the HTL quark and gluon mass parameters. The quark and gluon HTL mass parameters are determined self-consistently by a variational prescription. Combining the quark contribution with the two-loop HTL perturbation theory free energy for pure-glue we obtain the total two-loop QCD free energy. Comparisons are made with lattice estimates of the free energy for N_f=2 and with exact numerical results obtained in the large-N_f limit.Comment: 33 pages, 6 figure

Three-loop HTL gluon thermodynamics at intermediate coupling

We calculate the thermodynamic functions of pure-glue QCD to three-loop order using the hard-thermal-loop perturbation theory (HTLpt) reorganization of finite temperature quantum field theory. We show that at three-loop order hard-thermal-loop perturbation theory is compatible with lattice results for the pressure, energy density, and entropy down to temperatures $T\simeq3\;T_c$. Our results suggest that HTLpt provides a systematic framework that can used to calculate static and dynamic quantities for temperatures relevant at LHC.Comment: 24 pages, 13 figs. 2nd version: improved discussion and fixing typos. Published in JHE

Resummation in Hot Field Theories

There has been significant progress in our understanding of finite-temperature field theory over the past decade. In this paper, we review the progress in perturbative thermal field theory focusing on thermodynamic quantities. We first discuss the breakdown of naive perturbation theory at finite temperature and the need for an effective expansion that resums an infinite class of diagrams in the perturbative expansion. This effective expansion which is due to Braaten and Pisarski, can be used to systematically calculate various static and dynamical quantities as a weak-coupling expansion in powers of g. However, it turns that the weak-coupling expansion for thermodynamic quantities are useless unless the coupling constant is very small. We critically discuss various ways of reorganizing the perturbative series for thermal field theories in order to improve its convergence. These include screened perturbation theory (SPT), hard-thermal-loop perturbation theory (HTLPT), the Phi-derivable approach, dimensionally reduced (DR) SPT, and the DR Phi-derivable approach.Comment: 82 pages, 20 figures; v2 - typos corrected, references adde

Three-loop HTL QCD thermodynamics

The hard-thermal-loop perturbation theory (HTLpt) framework is used to calculate the thermodynamic functions of a quark-gluon plasma to three-loop order. This is the highest order accessible by finite temperature perturbation theory applied to a non-Abelian gauge theory before the high-temperature infrared catastrophe. All ultraviolet divergences are eliminated by renormalization of the vacuum, the HTL mass parameters, and the strong coupling constant. After choosing a prescription for the mass parameters, the three-loop results for the pressure and trace anomaly are found to be in very good agreement with recent lattice data down to $T \sim 2-3\,T_c$, which are temperatures accessible by current and forthcoming heavy-ion collision experiments.Comment: 27 pages, 11 figures; corresponds with published version in JHE

Late Gadolinium Enhancement Amount as an Independent Risk Factor for the Incidence of Adverse Cardiovascular Events in Patients with Stage C or D Heart Failure

Background: Myocardial fibrosis (MF) is a risk factor for poor prognosis in dilated cardiomyopathy (DCM). Late gadolinium enhancement (LGE) of the myocardium on cardiac magnetic resonance (CMR) represents MF. We examined whether the LGE amount increases the incidence of adverse cardiovascular events in patients with stage C or D heart failure (HF). Methods: Eighty-four consecutive patients with stage C or D HF, either ischemic or non-ischemic, were enrolled. Comprehensive clinical and CMR evaluations were performed. All patients were followed up for a composite endpoint of cardiovascular death, heart transplantation, and cardiac resynchronization therapy with defibrillator (CRT-D).Results: LGE was present in 79.7% of the end-stage HF patients. LGE distribution patterns were mid-wall, epi-myocardial, endo-myocardial, and the morphological patterns were patchy, transmural, and diffuse. During the average follow-up of 544 days, 13 (15.5%) patients had endpoint events: 7 patients cardiac death, 2 patients heart transplantation, and 4 patients underwent CRT-D implantation. On univariate analysis, LGE quantification on cardiac magnetic resonance, blood urine nitrogen, QRS duration on electrocardiogram, left ventricular end-diastolic diameter (LVEDD), and left ventricular end-diastolic volume (LVEDV) on CMR had the strongest associations with the composite endpoint events. However, on multivariate analysis for both Model I (after adjusting for age, sex, and body mass index) and Model II (after adjusting for age, sex, BMI, renal function, QRS duration, and atrial fibrillation on electrocardiogram, the etiology of HF, LVEF, CMR-LVEDD, and CMR-LVEDV), LGE amount was a significant risk factor for composite endpoint events (Model I 6SD HR 1.037, 95%CI 1.005–1.071, p = 0.022; Model II 6SD HR 1.045, 95%CI 1.001–1.084, p = 0.022). Conclusion: LGE amount from high-scale threshold on CMR increased the incidence of adverse cardiovascular events for patients in either stage C or D HF

Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance

This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.